Improved human cancer skin test. Membranes from cultured human melanoma cells infected with vesicular stomatis virus and UV inactivated gave markedly more sensitive skin test reactions in melanoma patients. 2. Methycholanthrene induced squamous cell carcinomas showed cross reacting tumor rejection antigens. This represents a new finding compared to previous reports that methylcholanthrene induced sarcomas do not have cross reacting antigens. 3. Mouse model for cancer vaccine preparations from tumor cells. Cell membrane preparations from influenza virus infected tumor cells induced strong tumor protection; membranes from non-infected tumor cells induced no tumor protection at all. The dose, route and timing of "virus-augmented" tumor cells membrane antigens to achieve optimum tumor immunity was determined. 4. Spontaneous neoplastic transformation in vitro is a modified form of foreign body tumorigenesis. Cultured cells such as Balb/3T3, C3H/10 1/2 or recently explanted adult subcutaneous connective tissue were not tumorigenic when inoculated subcutaneously in fluid suspension, but are definitely tumorigenic if inoculated attached to 1x5x10 mm plastic plates. BIBLIOGRAPHIC REFERENCES: Takeichi, N., Economou, G.C. and Boone, C.W.: Accelerated regeneration of trypsin-treated surface antigens of SV40 transformed BALB/3T3 cells induced by X-irradiation. Cancer Res., 36: 1258-1262, 1976. Boone, C.W., Takeichi, N., Paranjpe, M.S. and Gilden, R.: Vasoformative sarcomas arising from BALB/3T3 cells attached to solid substrates. Cancer Res., 36: 94-101, 1976.